I have rebound my right shift key (keycode 62) to act as the up arrow by replacing
Shift_R in its keysym with
$ xmodmap -e "keycode 62 = Up NoSymbol Up"
However when using the key, some applications (e.g. Firefox) still see it as a shift key - that is, when it is clicked it acts as both an up key and a shift key.
This means that when used in a textbox, instead of moving the cursor 1 line up, it moves the cursor 1 line up and highlights the text from the previous cursor position to the new cursor position, just like what would happen if you normally did Shift + Up.
How can I remove the Shift functionality from my right shift button, without removing it from the left shift key?